Pressure control apparatus



0 United States Patent [1113,548,865

[72] Inventor Bela P. Povinger 3,068,387 12/1962 Koppel l37/487.5X 15400Stansbury, Detroit, Mich. 48227 2,189,903 2/1940 How 137/426 [21] Appl.No. 689,148 2,261,300 11/1941 Smith, Jr. l37/486X [22] med 1967 PrimaryExaminer-M. Cary Nelson [45 1 Pammcd 1970 Assistant Examiner-Robert J.Miller Attorney-Walter Potoroka, Sr.

[54] PRESSURE CONTROL APPARATUS ABSTRACT: A chamber with ends definedgenerally by first lClllllJDnIlngFlgs.

and second variably positionable valves has a fluid (including 137/486,gases) pump connected thereto in a manner so as to place the 137/487.5,318/ second valve generally between the first valve and the pump. [51]31/04 As the pump runs a flow of fluid or gas through the chamber 605d7/03 is experienced and a reduction in pressure is experienced u betweenthe valves Difi'erential pressure responsive means 486,426, 501;318/28(Inq responsive to a reference pressure and the said reduction inpressure automatically causes the rotation of the second valve [56] ReamCM until a desired pressure is achieved in said chamber in order toUNITED STATES PATENTS obtain a desired predetermined pressuredifferential across 991,641 5/1911 Plantinga 137/501X the first valve.

PRGSSURE PRESSURE CONTROL APPARATUS BACKGROUND OF THE INVENTIONCarburetors for use in combination with internal combustion engines arerequired to emit fuel to the engine in a predetermined ratio to the airpassing through the carburetor and into the engine; However, in thesituations where the engine is employed in transportation vehicles theengine speed cannot remain constant and more often than not, the airfuel ratio has to be capable of change depending upon whether maximumeconomy or maximum power of the engine is desired. In order to beassured that a particular carburetor does provide proper air fuel ratiosfor varying engine operating conditions (reflected by the engine intakemanifold vacuum) the carburetor is first testedunder conditionssimulating such engine-operating conditions;

Heretofore it has been the practice to secure the carburetor onto a testfixture and to create an airflow through the carburetor inductionpassage past the carburetor throttle valve by means of a pump situateddownstream of the throttle valve. The pump speed would be varied inorder to create a vacuum simulating the engine manifold vacuum. Next,the quantity of air utilized was measured through the principle ofdisplaced volume. Finally, thequantity of fueli(or other liquid havingphysical characteristics much as those of gasoline fuel) dischargedthrough the carburetor is measured and the air fuel ratio determined bythese empirically determined quantities. All of these measurements aresusceptible to error. However, the greatest variant is the vacuumcreated by the pumps because its efficiency varies not only with pumpspeed but also with atmospheric and temperature variations.Consequently,

the finally determined air fuel ratios also vary because of thevariation in pump-created vacuum.

In view of the above, it is apparent that the variation in pumpefiiciency causes corresponding variations in the pressure differentialsacross the throttle valve of the carburetor being tested andconsequently the air fuel ratios determined thereby'continuously reflectsuch variations in undeterminable percentages of error.

SUMMARY OF THE INVENTION Pressure responsive means, responsive to thedifferential in pressures existing in the ambient atmosphere as well asthe interior of a chamber'having an inlet of variable effective area,delivers a signal in accordance with and reflective of said pressuredifferential to suitable motor means which varies the effective area ofan outlet of said chamber in order to attain and maintain apredetermined pressure difi'erential across said inlet. i 1

Accordingly a general object of this invention is to provide for use incombination with a chamber having an inlet of variable effective areaand an outlet of variable effective area experiencing a flow of fluidmedium therethrough, first means continuously responsive to the pressureupstream of the inlet and the pressure between the inlet and outlet forapplying a signal to suitable motor means effective "for'varying theeffective area of said outlet in order to maintain a preselectedpressure differential between said upstream pressure and the pressurebetween the inlet and outlet.

Another more specific object of this invention is to provide for use incombination with a flow-through chamber having an inlet and outlet ofvariable effective areas, electrical transducer means responsive to thedifferential in pressures as between the pressure upstream of said inletand outlet for providing an electrical signal to an electrical motorwhich in turn varies the effective area of said outlet in order toattain and maintain said pressure differential at a preselected value.

Other more specific objects and advantages of the invention will becomeapparent when reference is made to the following description consideredin conjunction with the drawings.

DESCRIPTION OF THE-DRAWINGS In the accompanying drawings:

cross section;

FIG. 5 is a wiring diagram illustrating a first modification of I thecircuitry shown in FIGS. 1 and 3; and

FIG. 6 if another wiring diagram illustrating another modification ofthe circuitry shown in FIGS. 1 and 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now in greater detailto the drawings, FIG. I illustrates, somewhat schematically, acarburetor I0 suitably mounted onto a test fixture 12 in a manner so asto have the carburetor induction passage (or passages if the carburetoris a multibarrel type) 14 in general alignment with an aperture 16formed in the fixture 12. A conduit 18, which might have a flange 20,has one end 22 situated so as to be in communication with aperture 16.The other end of conduit 18 is in communication with a vacuum (air) pump24. A butterfly valve 26, located within the conduit 18 between end 22and vacuum pump 24, is mounted for pivotal rotation within conduit 18 asby a rod or shaft 28. Shaft 28 is preferably rotated by a reduction gearwith a gearbox 30 which has an input from the shaft 32 of a directcurrent (DC) reversible motor 34.

A pressure-responsive transducer 36 is continuously responsive to twovariable pressure input signals one of which is accomplished as by aconduit 38 communicating at one end with transducer 36 and communicatingat its other end 40 with the interior of conduit 18 at a point generallybetween butterfly valve 26 and carburetor 10; The second signal ap pliedto transducer 36 is that of ambient atmospheric pressure as by conduitmeans 42.

Transducer 36 then, in accordance with the differential in pressurebetween ambient atmospheric pressure, P,, and the variable pressure, P,,in conduit 18 between carburetor l0 and butterfly valve 26 delivers avoltage, V,, which is proportional to said differential. The circuitrygenerally within a console 46 is comprised of first and second mainelectrical conductors 48 and 50 and a plurality of branch circuits 52,54, 56, 58, 60, 62, 64 and 66 connected thereacross. For example, branchcircuit 52 is comprised of an electrical conductor 520, connected tomain conductor 48, having an electrical contact 52b. A second conductor520, having a contact 52d is serially connected with a resistor 52a of amanually adjustable potentiometer 52f which has its other end connectedserially with a conductor 52g which, in turn, is electrically connectedto the other main conductor 50. A normally open relay-type switchcontact 52h is adapted to be at times moved into electrical en gagementwith contacts 52b and 52d so as to complete the circuitry therethrough.In each of the branch circuits 52, 54, 56, 58, 60, 62, 64 and 66 thevarious elements bearing a letter suf- V fix correspond to thoseelements of branch circuit 52 having a like suffix.

In addition to the above branch circuits, transducer 36 has one of itsterminals electrically connected to conductor 50 as by. a conductor 43.The other terminal of transducer 36 is electrically connected to oneterminalof an operational amplifier 84 by means of an electricalconductor 86.

A plurality of additional branch circuits 68, 70, 72, 74, 76, 78, and 82are electrically connected with conductor 44 and with wiper contacts52k, 54k, 56k, 58k, 60k, 62k, 64k and 66k of potentiometers 52f, 54f,56f, 58f, 60f, 62f, 64f and 66f.

Branchcircuit 68, for example, comprises a conductor 68a electricallyconnected'at one end to wiper contact 52!: and having a contact 68b atits other end. Another conductor 68c, having an electrical contact 68dat one end is connected at its other end to conductor 44. A normallyopen relay-type switch contact 682 is adapted to be at times moved intoelectrical engagement with contacts 68b and 68d so as to complete thecircuitry therethrough. In each of the additional branch circuits 68,70, 72, 74, 76, 78, 80 and 82 the various elements bearing a lettersufiix correspond to those elements of branch circuit 68 having a likesuffix.

A plurality of control circuits 88, 90, 92, 94, 96, 98, 100 and 102 areprovided for actuation of the normally open relaytype switches existingin both of .the previously described branch circuits. For example,control circuit 88 comprises an electrical conductor 88a connected atone end to a main conductor 104 and having a manually operable, normallyopen, switch member 88b. A first relay coil 88c surrounds the armatureportion of switch 680 and is electrically connected to a contact 88dadapted to be at times engaged by switch member 8812. A second relaycoil 882, surrounding the armature portion of switch 52h, may beseriallyelectrically connected at one end to coil 880 as by means of a conductor88f and connected at its other end by means of a conductor 88g to groundas at 38h. In each of the other control circuits 90, 92, 94, 96, 98, 100and 102, the various elements bearing a letter suffix correspond tothose elements of control circuit 88 having a like suffix. Further, asclearly shown, each of the control cir cuits is electrically connectedto the main conductor 104 one end of which is operatively connected to asource of electrical potential 106. The other side of electrical source106 is connected to ground potential as at 108.

Conductor 44 is electrically connected to anotherterminal of amplifier84 in order to apply a voltage differential to the amplifier 84 whensuch differential exists as between input conductors 86 and 44. Theamplifier then, in accordance with the voltage differential appliedthereto, directs an amplified voltage, of a particular value and signindicative of said differential, to terminal 110 of motor 34 by means ofan electrical conductor 112. The other terminal 114 of motor 34 may beconnected to ground 116 by a conductor 118.

OPERATION OF INVENTION Usually a maximum vacuum value of about l9.5inches of mercury (Hg) is required for testing a carburetor.Accordingly, pump 24 is selected so as to produce about 26 inches of Hgvacuum when the pump is run at a substantially constant speed assuggested by the manufacturer for optimum total pump efficiency. If thisis done then vacuum variation becomes a secondary issue because if therecommended pump running speed produces 26 inches of Hg vacuum,fluctuations of even $1.0 inches of Hg vacuum will reduce the minimumvacuum to only 25.0 inches of Hg vacuum which is still considerablygreater than the l9.5 inches of Hg vacuum required forcarburetortesting. FIG. 2 graphically illustrates both the nominal curve120, determined by the plotting of pump speed (r.p.m.) against cubicfeet of air per minute (c.f.m.) as well as the range of Hg vacuum valuesdetermined by the plotting of inches of Hg vacuum against cubic feet ofair per minute (c.f.m.). It can be seen that if the recommended pumpspeed is selected as indicated generally by line 122, that a value of 26inches of Hg vacuum may be obtained, and that variations of il .0 inchesof Hg vacuum will result in a maximum vacuum of 27 inches of Hg vacuumas indicated by dash line 124 and in a minimum value of 25 inches of Hgvacuum as indicated by dash line 126. The lowest or minimum value of 25inches Hg is still considerably higher. than the maximum value of 19.5inches of Hg required for carburetor testing.

Referring again to FIG. 1, an AC (alternating current) line voltage of,for example, a nominal voltage of l lv.-AC, is supplied by conductors128 and 130, which may include a switch member 132, to a stepdowntransformer-rectifier 138 which, for example, supplies a rectified 10.0v.-DC (direct current) at its terminals 136 and 138. As clearly shown,main conductors 48 and 50 are respectively electrically connected toterminals 136 and 138.

preferably, set to run at a substantially constant'speed recommended bythe manufacturer thereof as being that speed at which maximum pumpefficiency-is attained. Switch 132 is closed thereby completing thecircuit through conductors 128 and 130 to the transformer-rectifier 134which may be consideredas beinga bucking voltage supply. Further, switch140, serially connected in conductor .104 is also closed therebycompleting the circuit therethrough. However, the

normallyopen relay type switch members 52):, 54h, 56h, 58h, 60h, 62h,64h and66h (which may be spring-biased to the normallyopen position)preclude current flow through branch circuits 52, 54, 56, 58, 60, 62, 64and 66 respectively. Likewise, the normally openrelay-type switchmembers 68c, 70e, 72c, 74e, 76e, 78e, 802 and 82'e (which may also bespring-biased to the normally open position) preclude current flowthrough branch circuits 68, 70, 72, 74, 76, 78, and 82.

However, if at this time the manually operable switch 88b of controlcircuit 88 is closed, acircuit is completed from conductor 104 andthrough relay coils 88c and 88:: causing the respective armatures ofrelay switches to be pulled downwardly thereby causing switch member5211 to complete the circuit throughbranch circuit 52 and causing switchmember 68e to complete the circuit through branch circuit 68.Consequently, a closed circuit described by tenninal 138, conductor 50,conductor 52g, resistor 52e of potentiometer 52f, conductor 520,contacts 52d and 52b, switch member 52h, conductor 52a and conductor 48back to terminal 136 of the source of e.m.f. or powersupply 134. At thesame time a second circuit is establishedv bypotentiometer wiper contactdelivers an output voltage which is proportional to the differential inpressures sensed by the inputs through conduits 38 and 42 which, in thisinstance, are the ambient atmospheric pressure and the pressure with thechamber 47 generally defined by the conduit 18 and carburetor throttlevalve 15 at one end and the modulating valve 26 at the other end. The

output voltage from transducer 36 is transmitted as by a conductor 86 toanother input terminal of the operational amplifier 84.

The amplifier then amplifies the difference between the transduceroutput voltage, V,,and the output voltage of the potentiometer, V anddirects such amplified voltage, V to the input terminal of motor 34 asby conductor 112. The

other terminal of motor 34 may be connected to ground.

potential 1 16 as by a conductor 1,18.

The amplified voltage, V causes motor 34 to rotate shaft i 28 and thevalve 26 secured thereto in order to cause a sufficient restriction tothe flow of air so as to attain the desired pressure differentialacrosscarburetor throttle .valve 15. In this case it is assumed that19.5 inches of Hg vacuum (or pressure difierential) is desired acrossthrottle valve 15. If atmospheric conditions of time T, should change attime T,"

which is T, AT, the transducer 36 of course senses such changes and inaccordance therewith produces an output voltage V, such that I (Vt)T(YOT mentary differential voltage that by amplifier 84 will be amplifiedto (V causing the motor to rotate valve 26* in a direction to maintainthe selected pressure difierential across we throttle valve 15 ofcarburetor 10.

FIG. 3 illustrates a circuit typical of the circuit described above aswell as those established by the closing of any of switches 90b, 92b,94b, 96b, 98b, or l02b. For example, if the circuit of FIG. 3 isconsidered to be the equivalent of the circuit described by the closureof switches 88b, 52h and 68e then the battery 142 is equivalent to thebucking supply voltage source 134, conductors 144 and 146 respectivelyequivalent to conductors 50 and 43, resistor 148 and wiper contact 150respectively equivalent to resistor 52eand wiper contact 52k, andconductor 152 equivalent to conductor 48.

In view of the above it can be seen that a conventional current flow isestablished generally in a counterclockwise direction as indicatedgenerally by the path-defining arrows 154.

FIG. 3 clearly illustrates that if a voltage of, for example, 8.0 v.exists at wiper contact 150 and a voltage of, for example, 2.0 v. existsacross the transducer 36 then there is a voltage differential, V,,, of6.0 v. that the amplifier 84 is responsive to. In accordance with thedifferential of '6.0.,v. (amplified), the motor 34 is driven in a firstdirection causing the variably positioned valve 26 to rotate until thepressure within the chamber 47 is of a value which, as sensed by thetransducer 36, is sufficient for establishing the desired pressuredifferential across the carburetor throttle valve which-can beconsidered, in the broad sense, as being a variable restriction or anorifice of variableeffective area. If, on the other hand, only 1.0 v.existed at the wipercontact 150 while2.0 v. existed across thetransducer 36 then there is a voltage differential, V,,, of 1.0 v. thatthe amplifier 84 would be responsive to. Further, because the sign ofthe voltage is now reversed,,the amplifier would amplify the 1.0 v.differential, of opposite sign, causing the motor 34 to be driven in adirection opposite to the said first direction. Valve 26 would, ofcourse, as before be rotated until the transducer sensed the desiredpressure differential at which time there would be no voltagedifferential to be amplified by amplifier 84-.-(V,) V,,, i.'e. (V 1" 0.

The reason for the plurality of potentiometers in FIG. 1, as well as thecorresponding number of firstand second-branch circuits and controlcircuits is to enable the rapid selection of any of a plurality ofcorresponding pressure differentials across throttle valve 15. That is,each'of the wiper contacts 52k, 54k, 56k, 58k, 60k, 62k, 64k and 66k areso positioned along the respective resistors so that actuation of any ofthe control switches 88b, 90b, 92b, 94b, 96b, 98b, 100 b or l02b willcreate a base or reference voltage in conductor 44 which when matchedbythe voltage output of transducer 36 will result in a pressure withinchamber 47 which, in turn, will create the predetermined desiredpressure differential across throttle valve 15. In other words,potentiometer 52f may be set so that closure of switch member 88b-willresult in 19.5 inches of Hg pressure drop across throttle valve 15 whilepotentiometer 66f may be set so that closure of switch member 102b willresult in 0.5 inches of Hg pressure drop across throttle valve 15. Thewiper contacts on potentiometers 54f, 56f, 58f, 60f, 62f and 64f wouldbe respectively positioned along their corresponding resistors in orderto produce various pressure differentials between the previous values of19.5 inches of Hg and 0.5 inches of Hg as limits.

In'view of the preceding, it is apparent that any desired pressuredifi'erential can be established and maintained across the throttlevalve '15. The invention as considered in its broad aspects, providesfirst means for establishing a base reference voltage (the closure ofswitch member 88b or any one of the corresponding switch members and-theconcomitant closure of relay switches 52b and 68:), a chamber having atleast one inlet orifice of variable effective area (throttle l5, chamber47) and at least one outlet orifice of variable effective area (valve 26conduit 18), a first base pressure (a reference pressure such as theenvironmental pressure of ambient atmospheric pressure), meanscontinually responsive to the pressure within the chamber 47 and thebase pressure (transducer 36) for creating a voltage in accordance withthe differential thereof, means.(amplifier 84, motor 34) responsive tothe differential 'of said base reference voltage and said transducervoltage for varying the effective area of said outlet orifice to thateffective area whereby no differential exists as between said basereference voltage and said transducer voltage.

In addition to the preceding it has been discovered that the preferredembodiment of the modulating valve 26 takes the form of aprecision-built butterfly valve as illustrated generally in FIG. 1 andmore exactly in FIG. 4. As can best be seen in FIG. 4, the valve 26 issecured to the pivotally mounted shaft 28 joumaled for rotation as inthe wall of conduit 18. Preferably, valve 26 is formed so as tohave'upper and lower opposed convex surfaces 29 and 31 which meetgenerally at the periphery so as to define a circular periphery 33. Whenrotated from the position shown in FIG. 4, the outer periphery 33 wouldhave a configuration substantially as shown in phantom line. By havingthe surfaces 29 and 31 meet to define a somewhat knife-edge periphery33, the possibility of causing any turbulence or disturbance to theairstream is minimized. Additionally, the performa'nceof valve 26 can beenhanced and air turbulence further reduced by finishing the opposedsurfaces 29 and 31 so as to have a smooth surface finish. Further, ithas been determined that in an embodiment of valve 26 such as shown inFIG. 4, the gap between the outer periphery 33 of valve 26 and thecooperating interior diameter of pipe 18, when valve 26 is in its closedposition, should be in the order of 0.0005 inches.

The above is, of course, the preferred embodiment. It is apparent thatother valves and valving arrangements can be used to practice theinvention and that variables such as the flow velocity of the fluidmedium as well'as the weight-rate of flow become considerations in theselection of an appropriate valve configuration.

FIG. 5 illustrates a modification of the invention as shown in FIG. 1.Conductors 86 and 44 of FIG. 5 lead to the remaining circuitry asillustrated in FIG. 1; similarly shaft 28 is operatively connected tothe variably positioned valve 26 of FIG. I. The invention of FIG. 5operates in' the same manner as that of FIG. 1; however, an additionalbenefit is derived by having a DC tachometer generator 158 which isoperatively connected to motor 34 as by the pictorially representedcolinear shaft 160. Consequently, shaft 160 will rotate the tachometergenerator rotor and produce a voltage output, proportional to the speedof the motor 34, through a'conductor 162 to one of the input terminalsof a second amplifier '156. The other input terminal of the amplifier156 has connected thereto, as by a conductor l64,'the output of thefirst amplifier 84. The output of the second amplifier 156 is deliveredto terminal 110 of motor 34 as by aconductor 166. The voltage developedby the rotation of generator 158 is of such a sign as to diminish theeffective voltage amplified by amplifier 156. Consequently, the startingtorque of the motor remains at a minimum; however, when the speed of themotor starts to increase, a voltage signal is created by generator 158and fed back into the second amplifier so as to effectively diminish theotherwise normal output of the second amplifier. As a result of this,the action of the motor is somewhat damped thereby reducing the chancesof having the motor, because of increasing inertia, rotate valve 26beyond its proper position.

FIG. 6 illustrates another embodiment of the invention which is, ineffect, a modification of the voltage feedback arrangement of FIG. 5. Inthe arrangement of FIG. 5, instead of having a second amplifier, theoutput conductor 86 of transducer 36 is connected to one terminal 168 ofthe tachometer generator 158. Additionally, the resistor 170 of apotentiometer 172 has its ends respectively connected to terminals 168and 174 of tachometer generator 158. The potentiometer wiper contact 176is then electrically connected as by a conductor 178 to the other inputterminal'of the operational amplifier 84.

As in the embodiment of FIG. 5, the tachometer generator 158 produces avoltage of such a sign as to oppose the voltage output on conductor 86from transducer 36. The potentiometer 172 is provided for purposes ofadjustment if such is desired.

The feedback arrangements of both'FlGS. and 6 can be considered as theequivalent of viscous dampers in that it makes the overall system morestable. This becomes evident when it is remembered that the voltagefeedback signal from the tachometer generator increases in magnitude inaccordance with thespeed of the motor 34.

Although the invention herein has been disclosed and described withreference to its use in the testing of carburetors, it should beunderstood that the invention. is not so limited and can be employed forthe regulation of pressure differentials in any situation where a secondpressure is to be achieved and maintained in a particular predeterminedratio to a first pressure which, in turn, may or may not be stable.

Accordingly, even though only the preferred form and two .modificationsof the invention have been disclosed and existent within a chamberhaving an inlet of variably effective area and an outlet of variableeffective area, comprising first means for creating a base referencesignal indicative of a desired predetermined pressure differentialbetween said first and second pressures, second means continuallyresponsive to said first and second pressures and-effective forproducing a second signal proportionate to thedifferential of said firstand second pressures, third means responsive to the differential betweensaid base reference signal and said second signal and effective forvarying the effective area bf said outlet in order to vary the value ofsaid second pressure'to that pressure value which when compared to saidfirst pressure will'exhibit a pressure differential therebetweenequivalent to ,said, desired predetermined pressure differential, saidfirst means for creating said base reference signal comprising, aplurality of individual means each singly actuated and each so actuatedbeing effective to independently create abase reference signal the valueof which is different from the base reference signal created by theremaining means of said plurality of individual means.

